taru-adjective, adverb taking the 'to' particle
dim; vague; indistinct; faint; obscure
Literary word describing something visually or conceptually unclear, hazy, or blurred. Often used in written descriptions of scenery, memories, or outlines.
霧の中で山の輪郭が模糊としていた。
The outline of the mountain was dim in the fog.
彼の記憶は模糊として、はっきり思い出せなかった。
His memory was vague and he couldn't recall it clearly.
The kanji 模 and 糊 both relate to 'model' and 'paste', but the compound 模糊 is used in Chinese and Japanese to mean 'vague' or 'obscure'. The exact derivation is uncertain; it is a literary borrowing from Chinese.